newbie building a scratch-built computer

[Roy J. Tellason]

On Saturday 04 August 2007 17:42, Tony Duell wrote:
> > Thanks for all the information everyone. I'm really looking into
> > everything now, as far as building a computer from an off the shelf CPU
> > such as a Z80 or 6502. One thing that has occurred to me is that I will
> > likely need an EPROM Burner. Where can I get such a device for a modern
> > PC?
>
> IMHO, more important than the EPROM programmer is an EPROM emulator. This
> is a box of RAM that connectes to the EPROM socket of the target system
> (the board you'be just made) and also to a host machine (PC,  parallel
> port, serial port, USB?). YOu can quickly download perogams into the
> emulator, which then appears exactly as the EPROM does ot the target, and
> the latter can therefroe run said programs.

Agreed.

> The advantage over using EPROMs is that you can re-write the RAM as many
> times as you like (EPROMS have a limited number of program cycles) and
> rewrite it quickly. Unless your programming is a lot better than mine,
> you will go mad if you have to wait 20 minutes for an EPROM to be erased
> and reprogammed. each time you want to make a change!

Unless you have a pile of EPROMs handy...   :-)

> There have bnen seceral desings for such devices in Elektor magazine over
> the years (and I guess elesewhere). The one I put together (using the
> Elektor PCB) was just a handful of TTL parts and a couple of 32K SRAMs.
> It links to a PC parallel port (which downloads bytes into the RAM).

I remember seeing one magazine article for such a device,  but I wasn't that 
thrilled with the design of it. It used some sort of counter chips to step 
through the addresses of the target RAM,  and wasn't very flexible in its 
approach to things.

I started giving some serious thought to building one of those boxes, but 
never did finish it.

Do you know of designs on the web?

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
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Information is more dangerous than cannon to a society ruled by lies. --James 
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